Particle beam system and method for operating the same

ABSTRACT

A method of operating a particle beam system includes determining a deflection amount and a deflection time of a beam deflection module connected to a data network. The method also includes determining an un-blank time of a beam blanking module connected to the data network, and determining a blank time of the beam blanking module connected to the data network. The method further includes generating a data structure which includes plural data records, wherein each data record includes a command representing an instruction for at least one of the modules, and a command time representing a time at which the instruction is to be sent to the data network. In addition, the method includes sorting the records of the data structure by command time, and generating a set of digital commands based on the data structure. Moreover, the method includes sending the digital commands of the set to the network in an order corresponding to an order of the sorted records.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. §119(e)(1) toU.S. Ser. No. 61/541,154, filed on Sep. 30, 2011. The presentapplication also claims priority under 35 U.S.C. §119 to European patentapplication serial number 11 007 980.3, filed on Sep. 30, 2011. Thesecontents of these applications are hereby incorporated by reference intheir entirety.

FIELD

The disclosure relates to charged particle beam systems and methods ofoperating charged particle beam systems. The disclosure particularlyrelates to performing line scans using a charged particle system.

BACKGROUND

Conventional charged particle beam systems typically include a beamsource and a focusing lens to direct the charged particle beam onto anobject, a beam blanker to blank and un-blank the beam and a beamdeflector to scan the beam across the object. Charged particle beamsystems may further include a detector to detect charged particlesand/or radiation emerging from the object due to the incident beam.Using the detector, images of the object can be generated by scanningthe beam across the object and associating detected particle intensitieswith corresponding scan locations. Scanning of the beam across theobject typically includes performing a plurality of line scans, whereinthe location of incidence of the beam on the object is continuouslymoved along straight paths. A line scan is typically initiated by atrigger signal. Other desired actions, such as starting the scandeflection, ending the scan deflection, un-blanking the beam, blankingthe beam, starting data acquisition and stopping data acquisition, areelectronically controlled relative to the trigger signal by providingadjustable delay circuits in the respective electronic circuitscontrolling the beam deflector, the beam blanker and the dataacquisition, respectively. Other charged particle systems can be used,for example for writing patterns on the object by deflecting the beam toa location within a pattern feature to be written, un-blanking the beamand further deflecting the beam such that it is incident on otherlocations within the pattern feature.

SUMMARY

The disclosure is based, in part, at least, on the realization thatadjusting multiple electronic delay circuits for performing variousoperations can be tedious, lacking in reproducibility and inflexible.

According to embodiments of the present disclosure, a method ofoperating a particle beam system includes digitally controlling a firstdigitally controlled module of the particle beam system and a seconddigitally controlled module of the particle beam system, sending digitalcommand data to the first and second digitally controlled modules,wherein the digital command data includes at least a first command forthe first digitally controlled module and a second command for thesecond digitally controlled module, wherein the digital command data isgenerated based on information representing a time when the firstcommand is to be executed by the first digitally controlled module andon information representing a time when the second command is to beexecuted by the second digitally controlled module. The first and seconddigitally controlled modules can, in particular, be any of a beamdeflector and a beam blanker, a first and second beam deflectors, a beamdeflector and a signal detector, and a beam blanker and a signaldetector.

According to some embodiments, a method of operating a charged particlebeam system includes determining at least one deflection amount and atleast one deflection time, generating a first digital commandrepresenting an instruction for a beam deflection module of the particlebeam system connected to a data network of the particle beam system toprovide the at least one deflection to a charged particle beamcorresponding to the deflection amount, and sending the digital commandto the data network such that the beam deflection module can receive thedigital command data in order to perform the instructed operations, i.e.to provide the deflection corresponding to the deflection amount at thedeflection time.

The method may further include determining a beam un-blank time and abeam blank time, generating second digital command data instructing abeam blanking module of the charged particle system and connected to thedata network to un-blank the charged particle beam at the beam un-blanktime and to blank the charged particle beam at the beam blank time andsending the second digital command data to the data network such thatthe beam blanking module can receive the digital command data in orderto perform the instructed operations.

According to particular embodiments, the method may further includegenerating a data structure including plural data records, wherein eachdata record includes a command representing an instruction for at leastone of the beam deflection module and the beam blanking module, and acommand time representing a time at which the instruction is to be sentto the data network; sorting the records of the data structure bycommand time; and sending a set of digital commands encoding thecommands included in the data records to the network in an ordercorresponding to an order of the sorted records.

According to some embodiments, the method includes determining first andsecond deflection amounts and first and second deflection times. Forexample the first and second deflection amounts and times may be used toinstruct a line scan, starting at the first deflection time with thefirst deflection amount and ending at the second deflection time withthe second deflection amount, wherein the deflection is changedcontinuously or in discrete steps during the time period between thefirst deflection time and the second deflection time.

According to particular embodiments herein, at least one digital commandof the set represents a combined instruction for the beam deflectionmodule to provide a deflection to the beam corresponding to the firstdeflection amount and to subsequently provide a deflection to the beamcorresponding to the second deflection amount. The at least one digitalcommand may include, for example, at least one data element representinga time difference between the second deflection time and the firstdeflection time. Also, the at least one digital command may include atleast one data element representing at least one of a deflection stepsize by which the first beam deflection module is to change thedeflection of the beam in subsequent time steps, and a number of stepsin which the first beam deflection module is to change the deflection ofthe beam between the first deflection time and the second deflectiontime.

According to further embodiments, the method further includesdetermining a data acquisition start time and a data acquisition stoptime, generating digital commands instructing a data acquisition moduleof the charged particle system and connected to the data network tostart collecting data representing detected particle intensities at theacquisition start time and to stop collecting digital signalsrepresenting the detected particle intensities at the acquisition stoptime and sending these digital commands to the data network such thatthe data acquisition module can receive the digital command data inorder to perform the instructed operations. One or more data records ofthe sorted data structure may then include a command representing acorresponding instruction for the data acquisition module.

The data network is, within the present disclosure, a communicationdevice supporting transfer of digital data between modules connected tothe communication device. The network can be configured to have aparticular topology, such as, for example, point-to-point, bus, star andring.

According to certain embodiments, the set of digital command data isgenerated such that at least one digital command of the set representsboth an instruction for the beam deflection module to provide thedeflection to the beam corresponding to the deflection amount and aninstruction for the beam blanking module to un-blank the beam. Inexemplary embodiments herein, plural digital commands instructingdifferent modules to change their state, such as the beam deflectionmodule to change the provided deflection or the beam blanking module tochange from blanking the beam to un-blanking the beam, may also containinstructions for other modules to maintain their state. These latterinstructions have no effect on the other modules, but allow for auniform format of the digital commands and easy distribution to themodules connected to the network in a broadcast type protocol.

Individual digital command data sent across the network can be sent asone packet, or they can be split to fit into plural packages.Irrespective of whether individual command data are split into pluralpackages or not, they can be represented as a buffer or a set of pluralbits representing one or more data elements. In an individual digitalcommand data buffer, at least one data element identifies a command tobe performed by the addressed module connected to the network. Forexample, the data element may represent the command “un-blank the beam”or “blank the beam” for execution by the beam blanker, or “start scan”or “stop scan” for execution by the beam deflector. The digital commanddata may further include one or more data elements representing commandparameters providing additional information for execution of aparticular command. For example, the command “start scan” may beaccompanied by one or more parameters representing a duration of thescan or a number of scanning steps and a time duration for which thebeam should remain at a same scan position during the scan.

According to embodiments, the present disclosure provides a particlebeam system including at least a first digitally controlled module, asecond digitally controlled module, and an encoding module configuredgenerate digital command data, wherein the digital command data includesat least a first command for the first digitally controlled module and asecond command for the second digitally controlled module, wherein thedigital command data is generated based on information representing atime when the first command is to be executed by the first digitallycontrolled module and on information representing a time when the secondcommand is to be executed by the second digitally controlled module. Thefirst and second digitally controlled modules can, in particular, be anyof a beam deflector and a beam blanker, a first and second beamdeflectors, a beam deflector and a signal detector, and a beam blankerand a signal detector.

According to an exemplary embodiment, a particle beam system includes acharged particle beam source configured to generate a charged particlebeam; a data network; a beam blanking module connected to the datanetwork and configured to blank and un-blank the charged particle beam;a focusing lens configured to focus the charged particle beam onto anobject; a beam deflection module connected to the data network andconfigured to deflect the beam; a calculation module configured todetermine a deflection time, a beam un-blank time and a beam blank time,to generate a data structure including plural data records, wherein eachdata record includes a command representing an instruction for one ofthe beam deflection module and the beam blanking module, and a commandtime representing a time at which the instruction is to be sent to thedata network, and to sort the data records of the data structure bycommand time; and an encoding module configured to generate a set ofdigital commands encoding the commands included in the data records andsending the generated digital commands to the network in an ordercorresponding to an order of the sorted records.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing disclosure as well as other advantageous features will bemore apparent from the following detailed description of exemplaryembodiments with reference to the accompanying drawings. It is notedthat not all possible embodiments necessarily exhibit each and every, orany, of the advantages identified herein.

FIG. 1 is a schematic illustration of a charged particle beam systemaccording to an exemplary embodiment;

FIG. 2 is a chart illustrating a time sequence of operations of controlmodules of the system shown in FIG. 1 to perform a line scan;

FIG. 3 is a schematic illustration of control modules involved inperforming an operation of the system shown in FIG. 1;

FIGS. 4 a and 4 b are schematic representations of command data used forcommunication between control modules shown in FIG. 3;

FIG. 5 is a schematic illustration of a charged particle beam systemaccording to a further exemplary embodiment; and

FIG. 6 is a flowchart illustrating a method of controlling the chargedparticle beam system shown in FIG. 5.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

In the exemplary embodiments described below, components that are alikein function and structure are generally designated by alike referencenumerals. Therefore, to understand the features of the individualcomponents of a specific embodiment, the descriptions of otherembodiments and the summary may be referred to.

FIG. 1 is a schematic illustration of an embodiment of a particle beamsystem, which is an electron microscope in the illustrated example. Theparticle beam system 1 includes a particle beam source 3 including acathode 5, a suppressor electrode 7 and an extractor electrode 9 forgenerating an electron beam 11. The electron beam 11 emerging from anopening in the extractor electrode 9 is accelerated by an anode 13 to apredetermined kinetic energy and enters a beam tube 15 via an opening inthe anode 13.

The electron beam may traverse a condenser lens 17, an aperture 19provided in an electron detector 21. The electron beam further traversesan objective lens 23 for focusing the electron beam 11 at a location 25in an object plane 27 of the objective lens 23. A surface of an object29 which is to be inspected or manipulated with the particle beam system1 can be arranged in the object plane 27. The objective lens 23 includesan annular coil 31, which is arranged in an annular pole piece 33, whichincludes an annular upper pole piece 35 and an annular lower pole piece37 such that a magnetic field focusing the electron beam 11 is generatedin an annular gap between the two pole pieces 35 and 37. The objectivelens further includes a terminal electrode 39 which is arranged spacedapart from a lower end 41 of the beam tube 15 and has an openingtraversed by the electron beam 11. An electric field generated betweenthe lower end of the beam tube 41 and the terminal electrode 39decelerates the electrons, propagating inside the beam tube 15 at a highkinetic energy, to a desired lower kinetic energy at which they areincident on the object 29. This electric field may provide an additionalfocusing effect together with the magnetic field.

The individual components of the particle beam system 1 are controlledby a controller 42. The controller is shown in FIG. 1 as a functionalblock and includes plural control modules which can be spatiallyseparated from each other or arranged together in, for example, ahousing. Also, one or more of the plural control modules can be embodiedas individual electric circuits, and/or they can be embodied as softwaremodules running on a suitable processor, such as a general purposeprocessor, together with other control modules or modules performingother tasks, such as providing a user interface to the system 1.

One module of the controller 42 controls the beam source via connectors43 for supplying a heating current to the cathode 5 and defining apotential of the cathode. Electric potentials of the suppressorelectrode 7 and the extractor electrode 9 are controlled via connectors44. An electric potential of the beam tube 15 and the anode 13 isdefined by the controller via a connector 45. For this purpose, thecontroller 42 includes a stabilized high voltage source, which suppliesa voltage of, for example, 8 kV with respect to ground to the connector45.

Beam deflectors 47 which are controlled by a beam deflection module ofthe controller 42 via connectors 48 can be arranged in the objectivelens 23. The beam deflectors can be magnetic beam deflectors which mayprovide adjustable deflecting magnetic fields within the beam tube 15 inorder to vary the location 25 at which the electron beam 11 is incidenton the object 29, and to scan the particle beam 11 across a portion ofthe surface 27 of the object 29.

The particle beam 11 incident on the object 29 causes secondaryelectrons or backscattered electrons to emanate from the object 29. Aportion of these electrons may enter the beam tube 15 and can bedetected by the electron detector 21.

An exemplary trajectory of a secondary electron incident on the electrondetector 21 is labeled with reference numeral 51 in FIG. 1. Detectionsignals triggered by incident electrons are output by the electrondetector 21 at a connector 53 and can be read in by a data acquisitionmodule of the controller 42.

The particle beam source 3 is preferably operated in a stationary mode,i.e. once it is put into operation, the particle beam source 3 isoperated for several hours or even days under constant conditions suchthat the electron beam 11 is continuously generated. However, it isdesirable to not allow the electron beam 11 to be constantly incident onthe object 29 and to be able to switch the beam on and off as desired.For this purpose the particle beam system 1 includes a beam blankersystem 55 which includes a pair of deflector electrodes 56, 57 which canbe arranged inside the beam tube 15 such that the electron beam 11traverses a gap formed between the deflector electrodes 56, 57. Thecontroller 42 includes beam blanking module which supplies electricpotentials to the deflector electrodes 56, 57 via connectors 58 and 59.

If both deflector electrodes 56, 57 are at the same electric potential,the beam 11 traverses the gap between the deflector electrodes along astraight line. Preferably, the deflector electrodes are at a sameelectric potential as the beam tube 15.

If the deflector electrodes 56, 57 are at different electric potentials,an electrostatic field is produced between the two deflector electrodes.This electric field deflects the electron beam 11 away from its originaltrajectory. The deflected electron beam is shown in FIG. 1 as a brokenline 11′ and is incident on a plate 61 arranged in the beam tube 15. Theplate 61 has an aperture 62 which is traversed by the non-deflected beam11 to be incident on the surface 27 of the object 29. The electron beam11′ incident on the plate 61 is absorbed and cannot reach the surface 27of the object 29.

FIG. 2 shows charts illustrating a time sequence of actions performed bythe beam deflection module, the beam blanking module and the dataacquisition module of the controller 42. These actions are performedwithin a procedure to record an image using the electron microscopeshown in FIG. 1. Recording an image involves recording plural lines ofimage information by scanning the beam along lines and recordingcorresponding detected particle intensities. The particular actionsillustrated in FIG. 2 are related to performing one such line scan.

Chart (a) represents a current I supplied to the beam deflectors independence of time. This current is at a constant first level 101 inorder to provide a deflection corresponding to a first deflection amountin the beginning. The beam scanning starts at a time Tss and stops at atime Tse, such that the current is at a different constant second level105 in order to provide a deflection corresponding to a seconddeflection amount after time Tse. Between times Tss and Tse, acontinuous increase of the current level occurs, as indicated byreference numeral 106, in order to continuously change the provideddeflection such that a line scan is performed in the time period betweentimes Tss and Tse. The currents according to lines 101, 106 and 105 aregenerated by the beam deflection modules upon receipt of correspondingcommands. A command to start the scanning is sent to the network andreceived by the beam deflection module at a time Tcss before time Tss. Atime difference δT which is the difference between time Tss and Tcsscorresponds to an internal processing time of the beam deflectionmodule. This processing time δT is predetermined and known, such thatthe time Tcss can be suitably selected such that the physical beginningof the beam deflection occurs at time Tss. Similarly, a command to stopthe scanning is sent to the network and received by the beam deflectionmodule at a time Tcse. Again, time Tcse is earlier than time Tse,wherein a time difference δT between time Tse and time Tcse, accountsfor a processing time for the beam deflection module to stop scanning.This processing time δT subsequent to Tcse may have a same duration or adifferent duration than the processing time δT subsequent to Tcss.

Chart (b) illustrates a time dependency of a voltage applied to theelectrodes 56, 57 of the beam blanker. In this example, the un-blankingof the beam occurs at a time Tub, and the blanking of the beam occurs ata time Tb. Since the beam blank module needs some time to executereceived commands and to change the voltages applied to the electrodes,corresponding commands are sent to the network and received by the beamblanking module at earlier command times Tcub and Tcb, respectively.Herein, a time difference δT1 between Tub and Tcub can be longer thanthe time difference δT2 between Tb and Tcb. Blanking the beam involvesdeflecting the beam traversing the aperture 62 by a small amount suchthat it is incident on the plate 61. This can be quite fast since thebeam is un-blanked even before the deflection of the beam provided bythe deflector 56,57 has settled to a stable value. On the other hand,un-blanking the beam involves directing the beam, which is initiallyincident on the plate 61, such that it exactly traverses the aperture 62after the deflection of the beam provided by the deflector 56,57 hassettled to a stable value. This may involve relatively more time.Exemplary values for δT1 and δT2 can be within a range, for example,from 50 ns to 300 ns. In particular, δT1 and δT2 can have differentvalues. For example, δT1 can be longer than δT2.

According to some embodiments, the time difference between the blanktime and the un-blank time differs from the time difference between thesecond command time and the first command time by more than 50 ns, morethan 100 ns or more than 200 ns.

The time Tub at which the beam is un-blanked is, in the illustratedexample, earlier than the time Tss at which the beam deflection modulestarts the scan. This is due to a time for the particles to travelbetween the electrodes 56, 57 of the beam blanker and the deflectioncoils 47 of the beam deflector. Due to this traveling time, the beamblanker is operated earlier than the beam deflector. Similarly, the timeTb at which the beam blanker blanks the beam, is earlier than the timeTse at which the beam deflection module stops scanning the beam.

Chart (c) illustrates an operation of the data acquisition module of thecontroller 42. The detector 21 continuously produces analog detectionsignals irrespective of whether the beam is blanked or un-blanked orscanned. To record an electron microscopic image of an object, detectedparticle intensities are associated with scanning locations of the beamat the time of recording, i.e. with locations of the object. For thispurpose, it is desired to collect a sequence of data values representingdetected particle intensities, wherein the sequence starts when thescanning beam is at a corresponding starting position, corresponding to,for example, a left image margin, and the sequence stops when thescanning beam is at a different position corresponding, for example, toa right image margin. The starting and stopping of the data acquisitionis synchronized with the scanning of the beam, wherein the dataacquisition is delayed relative to the beam deflection due to times forthe primary particles to travel from the deflector to the object and thesecondary particles to travel from the object to the detector. As shownin chart (c) the data acquisition module starts collecting the digitalimage data at a time Tas which is later than the time Tss at which thebeam deflection module starts scanning. Similarly, the data acquisitionmodule stops data acquisition at a time Tae which is later than time Tseat which the beam deflection module stops scanning. Again, since thedata acquisition module involves some processing time for executingcommands, a command for instructing the data acquisition module to startcollecting data is sent to the network and received by the dataacquisition module at a time Tcas which is earlier than Tas, and acommand for instructing the data acquisition module to stop collectingdata is sent to the network and received by the data acquisition moduleat a time Tcae which is earlier than Tae.

Chart (d) illustrates the time sequence of the commands illustratedabove for the present exemplary embodiment:

-   Tcub<Tcss<Tcas<Tcb<Tcse<Tcae.

According to other embodiments, other time sequences are possible,depending on, for example, traveling times of particles in the systemand processing times of the individual modules.

FIG. 3 is a schematic illustration of a portion of the controller 42used for controlling the beam blanker, beam deflector and dataacquisition. For this purpose, the controller 42 includes a calculationmodule 111 which determines the times Tub, Tss, Tas, Tb, Tse, Tae basedon plural parameters. Some parameters are received via an interface 113,which can be an interface to a local area network or a keyboardconfigured to receive data representing the task to be performed, suchas left and right boundaries of an image to be recorded, a pixel speed,an image resolution and other parameters. The calculation performed bythe module 111 may take a considerable amount of processing time andtakes into account other parameters representing physical properties ofthe charged particle beam system, such as a kinetic energy and a speedof the charged particles in order to calculate corresponding travelingtimes, and other parameters.

As soon as the module 111 has completed the calculation of the timesTub, Tss, Tas, Tb, Tse, Tae, the corresponding earlier command timesTcub, Tcss, Tcas, Tcb, Tcse, Tcae are calculated based on the processingtimes used by the respective modules executing the commands. Datarepresenting the Tcub, Tcss, Tcas, Tcb, Tcse, Tcae and additionalcommand parameters are transmitted to a command generation module 115which encodes the commands and additional parameters into digitalcommand data suitable to be sent to the corresponding modules across anetwork 117. The module 115 also supplies the generated command data tothe network 117 according to the time sequence illustrated in chart (d)of FIG. 2. For this purpose, the module 115 receives a clock signal froma clock 119. The same clock signal is also supplied to components of thenetwork 117 and a beam blanking module 121 to which the electrodes 56,57 of the beam blanker are connected, a beam deflection module 123, towhich the beam deflector 47 is connected, and a data acquisition module125, to which the detector 21 is connected. The data collected by thedata acquisition module 125 are supplied to an image memory 127.

The beam blanking module 121, the beam deflection module 123 and thedata acquisition module 125 are connected to the network 117 such thatthey can receive the commands supplied by the module 115. The modules121, 123, 125 are configured to execute corresponding actions uponreceipt of the commands from the network 117. In the presentillustration, it is assumed, that the time between sending a command tothe network and the reception of the command by the respective module isnegligible. However, if this assumption is not sufficiently accurate inpractice, a time for the commands to travel across the network can betaken into account when the times Tcub, Tcss, Tcas, Tcb, Tcse, Tcae arecalculated based on the times Tub, Tss, Tas, Tb, Tse, Tae.

FIG. 4 a schematically shows an exemplary layout of data elements withina data buffer encoding an exemplary command. The data buffer includes anumber of n bits with low order bits located on the left in FIG. 4 a andhigh order bits located to the right in FIG. 4 a. A first number ofconsecutive bits 141 represents an address within the network of thedestination module of the command. Depending on a topology of thenetwork, such address can be omitted. For example, a network havingpoint-to-point topology, would not require that an address of theaddressed module is included in the command.

A second number of consecutive bits 143 represents the command. In theillustrated example, the command is “begin scanning” instructing thebeam deflection module to start scanning.

A third number of consecutive bits 145 form a data element representinga command parameter. In the illustrated example, this command parameteris the duration of the scan and instructs the beam deflection module tostop scanning after this duration. As a consequence a separatesubsequent command separately instructing the beam deflection module tostop scanning is not necessary. The two commands instructing the beamdeflection module to start scanning and instructing the beam deflectionmodule to stop scanning are combined into a single combined command,accordingly. According to other examples, such combined commands are notused, and separate commands are generated starting and stopping thescanning, wherein a data element representing the duration of the scanneed not to be included in the command data.

A fourth number of consecutive bits 147 form a data element representinga further command parameter which is a number of scanning steps to beperformed between start of the scan and end of the scan. Thus, thisparameter determines the image resolution to be achieved with the scan.

FIG. 4 b schematically shows another exemplary layout of data elementswithin a data buffer encoding plural commands. The data buffer includesa number of m bits with low order bits located on the left in FIG. 4 band high order bits located to the right in FIG. 4 b.

A first number of consecutive bits 149 represents the command for thebeam blanking module to either blank or un-blank the beam. For example,this command can be encoded by one single bit.

A second number of consecutive bits 151 represents the command for thedata acquisition module to either collect data or to not collect data.Also this command can be encoded by one single bit.

A third number of consecutive bits 153 represents the command for thebeam deflection module to provide a deflection to the beam correspondingto a given deflection amount. The deflection amount can be encoded, forexample, by two sub-groups 155 and 157 of consecutive bits within thethird number of consecutive bits 153, wherein sub-group 155 encodes thedeflection in an x-direction and sub-group 155 encodes the deflection inan y-direction of the deflection module.

The data buffer can be broadcasted simultaneously to all modules, i.e.the beam deflection module, the beam blanking module and the dataacquisition module, wherein the beam blanking module extracts bits 149from the data buffer and process these bits as a received command, thedata acquisition module extracts bits 151 from the data buffer andprocess these bits as a received command, and the beam blankingdeflection module extracts bits 153 from the data buffer and processthese bits as a received command.

If, with such layout, the state of only one module has to be changed bya command, it is sufficient to generate the command for this modulebased on the desired change, and it is easy to generate the commands forthe other modules such that they are identical to previous commands tothose modules or to the current states of these modules. If, forexample, a first command includes an instruction for a beam blankingmodule to un-blank the beam and a subsequent command includes aninstruction for a beam deflection module to start a line scan while thestate of the beam blanking module should remain un-changed, i.e.un-blanked, the subsequent command may contain a repeated instruction toun-blank the beam, since such repeated instruction will not change thecurrent state of the beam blanker. If, according to another example, afirst command includes an instruction for a beam deflection module tostart a line scan and a subsequent command includes an instruction for abeam blanking module to un-blank the beam while the state of the beamdeflection module should remain un-changed, i.e. the beam deflectorshould continue with the line scan, the subsequent command may contain anew instruction for the beam deflection module to start a line scan,wherein the parameters of the new line scan are selected such that thenew line scan steadily continues the previous line scan withoutinterruption.

It is apparent that many variations of the command data layoutillustrated in FIGS. 4 a and 4 b are possible.

FIG. 5 is a schematic illustration of an embodiment of a particle beamsystem which is an ion beam system in the illustrated example. The ionbeam system 1 includes an ion source 3 and electrodes 7 and 9 forextracting ions from the source 3 and accelerating the extracted ions togenerate an ion beam 11 which is collimated by a condenser lens 17. Thebeam 11 is further accelerated by an electrode 13 and traverses a beamblanker 55 including deflector electrodes 56 and 57, and a plate 61having an aperture 62 configured such that the beam 11 may traverse theaperture 62 when same electric potentials are applied to the electrodes56 and 57 and such that the beam 11 is incident on and absorbed by theplate 61 if different electric potentials are applied to the electrodes56 and 57.

An objective lens 23 configured to focus the ion beam 11 in an objectplane 27 is provided downstream of the beam blanker 55.

The ion beam system 1 further includes a first beam deflector 47arranged downstream of the beam blanker 55, and a second beam deflector47′ arranged downstream of the first beam deflector 47 and upstream ofthe objective lens 23. The beam deflectors 47 and 47′ are configured todirect the ion beam 11 to selected locations within the object plane 27.In the illustration of FIG. 5, the ion beam 11 is focused in the objectplane 27 at a distance d of an axis of symmetry 2 of the objective lens23. To achieve such deflection of the ion beam 11, the first deflector47 deflects the beam away from the axis of symmetry 2, and thesubsequent second deflector 47′ deflects the beam towards the axis ofsymmetry 2 such that the beam 11 traverses the objective lens 23 closeto its axis of symmetry, such that aberrations introduced by theobjective lens 23 are maintained at a relatively low level.

A secondary particle detector 21 is located close to the object plane 27such that secondary particles generated by the incident ion beam 11 canbe detected. A line 51 in FIG. 5 represents an exemplary trajectory ofan electron released from an object and incident on the detector 21.

The ion beam system 1 includes a controller for controlling theindividual components for generating and directing the ion beam 11 tothe object plane 27. Similar to the illustration of FIG. 1, thecontroller 42 is shown as a functional block including plural controlmodules which can be physically separated from each other and/or areembodied as software modules running on a suitable processor. Inparticular, the ion source 3 is connected to the controller 42 via aconnector 43 such that the controller 42 can energize and operate theion source 3. The electrodes 7, 9, 13 and 61 are connected to thecontroller 42 via connectors 44 and 45 such that the electric potentialsapplied to the electrodes can be adjusted by the controller 42.Similarly, connectors 49 are provided to connect lenses 17 and 23 to thecontroller 42 such that the controller 42 can supply suitable electricpotentials and currents to the lenses in order to collimate and focusthe ion beam 11.

The first and second beam deflectors 47 and 47′ each include a pluraldeflecting electrodes 46 distributed about the axis of symmetry 2. Thenumber of deflecting electrodes 46 can be, for example, two, fours,eight, as in the illustrated embodiment, or even more than eight. Thedeflecting electrodes 46 are connected to the controller 42 viaconnectors 48 such that the controller 42 can adjust angles andorientations of deflections provided by the deflectors 47, 47′ to theion beam 11.

Similarly, the detector 21 is connected to the controller 42 via aconnector 53 such that the controller can receive detection signalsproduced by the detector 21.

The controller 42 may have a configuration similar to that illustratedwith reference to FIG. 3 above. In particular, the controller 42 mayinclude an interface for receiving parameters of a task to be performedby the ion beam system 1, a calculation module configured to determinecommands and command parameters suitable for controlling the beamblanker 55, the first and second deflectors 47, 47′ and an acquisitionof measurement data via detector 21. The controller 42 may furtherinclude a command generation module for encoding the calculated commandsand command parameters into digital command data, and a network fordistributing the digital command data to control modules controlling thecomponents of the ion beam system 1, such as a beam blanking module, abeam deflection module for the first beam deflector 47, a beamdeflection module for the second beam deflector 47′ and a dataacquisition module for acquiring the measurement data from the detector21.

FIG. 6 is a flow diagram illustrating a method of controlling thevarious modules of the ion beam system 1.

In a step 201, parameters of a primary task are determined. In theillustrated example, the task is to scan the focused ion beam along astraight line on the sample and to record corresponding detectionsignals generated by the detector 21. The corresponding primary task isto control the first and second deflectors such that a voltage appliedto opposite deflections electrodes 46 of the first deflector 47 startsto rise from a given voltage level (position) at a time Tss1 with acertain rate (speed), and stops rising a at a time Tse1. A correspondingprocedure is defined for the second deflector 47′, wherein the positionsand speeds may vary between the deflectors since the second deflector47′ has to deflect the beam by a larger amount than the first deflector47. Also the start times and end times will vary between the deflectorsdue to a traveling time of the ions between the first deflector 47 andthe second deflector 47′. The parameters of the primary task can beentered by the user, or they can be generated by some software andsupplied to the controller 42 via its interface. The parameters of theprimary task can be represented by a data structure which is shown inFIG. 6 as a table 203, in which separate lines indicate separatecommands for operating components and in which the columns represent thetime when a given command is to be executed, a component performing thecommand, a command performed by the component and parameters of therespective command.

In a step 205, additional secondary tasks are determined which are usedto perform the primary task. For example, in order to start deflectionwith deflector 1 using a given voltage level (position) at time Tss1,the initial voltage level (position) is set at an earlier time Tss1−Δ,wherein Δ is selected such that the voltage applied to the pair ofelectrodes 46 has settled and is sufficiently stable at time Tss1. Asimilar procedure is applied to the second deflector. Moreover, the beamblanker is controlled to un-blank the beam at a time Tub which isearlier than the start of the deflection by deflector 1 due to travelingtimes of the ions between the beam blanker and the first deflector. Atime Tb for the beam blanker to blank the beam is also determined.Moreover, commands for starting the data acquisition at a time Tas andfor terminating the data acquisition at a time Tae is determined. Thetime Tas will be later than the time Tss1 for starting the deflectionwith the first deflector due to traveling times of the ions towards thesample and of secondary particles from the sample towards the detector21.

A data structure representing the commands after the secondary taskshave been added can be represented as a table 207, in which differentlines represent different commands and columns represent times,components, commands and parameters.

The step 205 of adding secondary tasks can be performed by thecalculation module of the controller 42.

Certain commands of the table 207 can be combined into combined commandsin a step 209. For example, the commands of instructing the firstdeflector to start deflecting at Tss1 and to stop deflecting at Tse1 canbe combined to a combined command which instructs the first deflector tostart deflection at Tss1 wherein a duration of the deflection is aparameter of the command. Similarly, the commands for starting andstopping the deflection of the second deflector and the commands forun-blanking and blanking the beam can be combined into combined commandshaving a duration as a parameter. A data structure representing thecombined commands can be represented as a table 211. The step 209 ofcombining tasks can also be performed by the calculation module of thecontroller 42.

In a step 213, some of the commands are corrected for delays by controlmodules and electronic components and circuits between receipt of therespective commands and start of execution of the commands. For example,the time Tss1 for starting the deflection with the first deflector iscorrected by a delay δtd by the deflection module to receive and analyzethe command and to set electronic circuits such as voltage generators inorder to perform the deflection. The corrected time Tcss1=Tss1−δdindicates the command time at which the command is to be sent to thenetwork such that the beam scanning starts at the time Tss1. Similarly,The command time Tcub for instructing the beam blanker to un-blank thebeam at Tub is determined by subtracting a delay δtb from Tub, and thecommand times Tcas and Tcae of the commands instructing the dataacquisition module to start and end data acquisition are determined bysubtracting a delay δta from Tas and Tae, respectively. In theillustrated example, the times Tss1−Δ and Tss2−Δ are not corrected foradditional electronic delays since the time Δ has been selected suchthat the initial voltages are set sufficiently ahead of the times Tss1and Tss2, respectively. The command times of these commands forinstructing the beam deflection module are equal to Tss1−Δ and Tss2−Δ,accordingly. A data structure representing the commands generated instep 213 is shown as a table 215 in FIG. 6. Also the step 213 can beperformed by the calculation module of the controller 42.

The commands generated in step 213 are sorted by command time in a step217 such that the commands are arranged according to their correspondingtimes. The sorted commands are shown as a table 219 in FIG. 6. Also thestep 217 can be performed by the calculation module of the controller42.

Thereafter, the commands are encoded into digital command dataassociated with a command schedule in a step 221. The digital commanddata of each command can be sent across the network to the receivingcontrol modules of the controller 42. The digital command data andschedule are represented as a table 223 in FIG. 6. The encoding of thecommands in step 221 can be performed by a command generating module ofthe controller 42 after having received the calculated commands from thecalculation module.

The command generation module will then send the sequence of digitalcommand data to the network at times defined by the schedule in a step225. A start time of sending the sequence of commands can be defined bya trigger signal generated by a clock or supplied separately. Thedigital command data are received by the beam blanking module, the beamdeflection modules and the data acquisition module from the network, andthe modules interpret the commands and control the beam blanker,deflectors and data acquisition components such that the commands areexecuted as desired.

In the example illustrated with reference to FIG. 6 above, each digitalcommand includes an instruction for one module of the charged particlesystem. According to other examples, the digital commands can begenerated such that some or all digital commands each includeinstructions for more than one module, as illustrated with reference toFIG. 4 b above.

In the examples illustrated above, the method of operating a particlebeam system using sorted commands sent to a network such that they arereceived by a beam deflection module and a beam blanking module are usedfor performing a line scan with the charged particle beam. However,these methods can also be used to perform other procedures with thecharged particle system, such as modifying a sample by deposition ofmaterial on or removal of material from a sample, which may be assistedby supplying a reactive gas to the sample, or writing a pattern into aresist. These procedures involve an operation of deflecting the beam toa target position on the sample and, when the beam has reached thetarget position, un-blanking of the beam such that a dose of chargedparticles is delivered to the surface of the sample in order to performthe action, such as removal of material, deposition of material andmodifying a resist. Depending on a configuration of the pattern, initialdeflections to deflect the beam such that it is directed to a targetposition within a particular pattern feature depends on a distance ofthis particular pattern feature from another pattern feature which waspreviously processed. For example, to move the beam from a previouslyprocessed pattern feature to a closely adjacent pattern feature involvesa relatively small deflection, whereas moving the beam from a previouslyprocessed pattern feature to a distant next pattern feature will involvea substantially larger amount of deflection. Depending on the deflectionamount, different settling times will be used after completion of thedeflection until the beam is stable and points to the desired targetlocation within the next feature. Generally, such settling times oradditional waiting times are greater for greater deflections. In orderto perform the desired action, such as writing a pattern, with a highaccuracy, the beam is un-blanked only after such settling time hasexpired. With the methods illustrated above, such additional andvariable waiting times can be easily achieved. According to an exemplaryembodiment in this context, the beam un-blank time is later than thedeflection stop time, and a time difference between the beam un-blanktime and the deflection stop time is variable. For example, this timedifference can be varied by more than 5 μs and 50 μs.

In the embodiments illustrated above, one particle beam column, such asan electron beam column shown in FIG. 1 and an ion beam column shown inFIG. 5 are controlled by using methods for generating digital commandsfor controlling modules of the particle beam column as illustratedabove. However, it is also possible to control modules distributedacross plural particle beam columns using such methods. For example, asystem including an electron beam column and an ion beam column can becontrolled with such methods, wherein various modules, such asdeflectors, beam blankers and detectors, of the two particle beamcolumns are connected to a common data network. The modules of the twoparticle beams may receive digital commands generated based on sorteddata records including commands representing instructions for theindividual modules. The digital commands can be generated by onecontroller, for example.

While the disclosure has been described with respect to certainexemplary embodiments thereof, it is evident that many alternatives,modifications and variations will be apparent to those skilled in theart. Accordingly, the exemplary embodiments of the disclosure set forthherein are intended to be illustrative and not limiting in any way.Various changes may be made without departing from the spirit and scopeof the present disclosure as defined in the following claims.

What is claimed is:
 1. A method of operating a particle beam system, themethod comprising: determining at least one deflection amount and atleast one deflection time at which a first beam deflection module of theparticle beam system connected to a data network of the particle beamsystem is to provide the at least one deflection to a charged particlebeam corresponding to the at least one deflection amount; determining anun-blank time at which a beam blanking module of the particle beamsystem connected to the data network is to un-blank the beam;determining a blank time at which the beam blanking module connected tothe data network is to blank the beam; generating a data structurecomprising a plurality of data records, each data record comprising acommand representing an instruction for at least one of the first beamdeflection module and the beam blanking module, each data record furthercomprising a command time representing a time at which the instructionis to be sent to the data network; sorting the data records by commandtime; generating a set of digital commands based on the data structure,one digital command being generated for each one of the data records;and sending the set of digital commands to the network in an ordercorresponding to an order of the sorted records, wherein: at least onedigital command of the set of digital commands represents an instructionfor the first beam deflection module to deflect the beam correspondingto the at least one deflection amount; at least one digital command ofthe set of digital commands represents an instruction for the beamblanking module to un-blank the beam; and at least one digital commandof the set of digital commands represents an instruction for the beamblanking module to blank the beam.
 2. The method according to claim 1,wherein at least one digital command of the set of digital commandsrepresents both an instruction for the first beam deflection module todeflect the beam corresponding to the deflection amount and aninstruction for the beam blanking module to un-blank the beam.
 3. Themethod according to claim 1, wherein at least one digital command of theset of digital commands represents both an instruction for the firstbeam deflection module to deflect the beam corresponding to thedeflection amount and an instruction for the beam blanking module toblank the beam.
 4. The method according to claim 1, comprisingdetermining first and second deflection amounts and first and seconddeflection times, wherein at least one digital command of the set ofdigital commands represents a combined instruction for the first beamdeflection module to deflect the beam corresponding to the firstdeflection amount and to subsequently provide a deflect the beamcorresponding to the second deflection amount.
 5. The method accordingto claim 4, wherein the at least one digital command comprises at leastone data element representing a time difference between the second andfirst deflection times.
 6. The method according to claim 4, wherein theat least one digital command comprises at least one data elementrepresenting at least one of: a) a deflection step size by which thefirst beam deflection module is to change the deflection of the beam insubsequent time steps; and b) a number of steps in which the first beamdeflection module is to change the deflection of the beam between thefirst deflection time and the second deflection time.
 7. The methodaccording to claim 1, wherein the un-blank time is later than thedeflection time, and a time difference between the beam un-blank timeand the deflection time is variable.
 8. The method according to claim 7,wherein the time difference between the un-blank time and the deflectiontime can be varied by more than 5 microseconds.
 9. The method accordingto claim 1, wherein: the data structure comprises a first data recordcomprising a command representing an instruction for the beam blankingmodule to un-blank the beam and a first command time representing a timeat which this instruction is to be sent to the data network; the datastructure comprises a second data record comprising a commandrepresenting an instruction for the beam blanking module to blank thebeam and a second command time representing a time at which thisinstruction is to be sent to the data network; and a time differencebetween the blank and un-blank times differs from a time differencebetween the second and first command times.
 10. The method according toclaim 9, wherein the time difference between the blank and un-blanktimes differs from the time difference between the second and firstcommand times by more than 50 nanoseconds.
 11. The method according toclaim 1, wherein: the data structure comprises at least one recordcomprising a command representing both an instruction for the beamblanking module to un-blank the beam and an instruction for the beamblanking module to blank the beam; and the at least one commandcomprises at least one data element representing a time differencebetween the blank and un-blank times.
 12. The method according to claim1, further comprising: determining a data acquisition start time atwhich a data acquisition module of the particle beam system connected tothe data network is to start collecting data representing detectedparticle intensities; and determining a data acquisition stop time atwhich the data acquisition module is to stop collecting data, wherein:at least one digital command of the set of digital commands representsan instruction for the data acquisition module to start collecting ofthe data; and at least one digital command of the set of digitalcommands represents an instruction for the data acquisition module tostop collecting of the data.
 13. The method according to claim 12,wherein at least one digital command of the set of digital commandsrepresents a combined instruction for the first data acquisition moduleto start collecting the data and to subsequently stop collecting thedata.
 14. The method according to claim 13, wherein the at least onedigital command comprises at least one data element representing a timedifference between the acquisition stop time and the acquisition starttime.
 15. The method according to claim 1, further comprisingdetermining at least one deflection amount and at least one deflectiontime at which a second beam deflection module of the particle beamsystem connected to a data network of the particle beam system is toprovide a deflection to a charged particle beam corresponding to thedeflection amount, wherein at least one digital command of the set ofdigital commands represents an instruction for the second beamdeflection module to provide the deflection to the beam corresponding tothe deflection amount.
 16. The method according to claim 1, wherein atleast one parameter is greater than one nanosecond, the at least oneparameter being selected from the group consisting of: a time differencebetween: a) the command time of the data record comprising the commandrepresenting the instruction for the first beam deflection module toprovide the deflection to the charged particle beam corresponding to thedeflection amount; and b) the deflection time; a time differencebetween: a) the command time of the data record including the commandrepresenting the instruction for the beam blanking module to un-blankthe beam; and b) the un-blank time; and a time difference between: a)the command time of the data record including the command representingthe instruction for the beam blanking module to blank the beam; and b)the blank time.